Telephone-exchange system



Jan. 3, 1928.

1,655,061 W. C. JORDAN TELEPHONE EXCHANGE SYSTEM Filed Aug. 28. 1926 2 Sheets-Sheet 1 J 1 H A Q 3* Q by W MAI/34 Jan. 3, 1928.

W. C. JORDAN TELEPHONE EXCHANGE SYSTEM led Aug. 28. 1926 rah/7 Patented Jan. 3, 1928.

UNITED STATES PATENT OFFICE.

WILLIAM C. JORDAN, OF MADISON, NEVI JERSEY, ASSIGNOR TO BELL TELEPHONE LABORATORIES, INCORPORATED, OF NEVI YORK, N. Y., A CORPORATION OF NEW YORK.

TELEPHONE-EXCHANGE SYSTEM.

Application filed. August 28, 1926.

This invention relates to automatic telephone exchange systems, and more particularly to improved means for testing called telephone lines prior to completing connections thereto.

Telephone lines appearing before final selectors are customarily identified as of one of two classes, viz, as individual lines and last lines of groups leading to private branch exchanges, or as other P. B. X. lines. This classification is usually indicated by the resistance connected in series with the sleeve terminal of the line in question. the resistance being less for last P. X. lines and individual lines, and greater for other P. B. X. lines. Final selectors have heretofore been equipped to apply asimultaneous test to distinguish bet-ween these classes or lines, and to determine the busy or idle condition thereof. It has been the practice to identity the sleeve terminals of idle lines with a ground potential and busy lines with battery potential. The testing means operated only in case a busy line was encountered; hence a line whose sleeve terminal was open or grounded accidentally would be treated as an idle line. Where final selectors ot the prior art have been used with means to cancel the test, in order that a connection might be completed with a busy line, the release of the selector has been dependent upon the disconnection of the called subscriber.

In accordance with the present invention the sleeve terminals of called lines are con-- nected to battery when idle and to ground when busy and an additional test is provided to distinguish busy lines and those accidentally grounded, the latter condition resulting in the. operation o1 an alarm. According to another aspect oi the invention the tests of the called line are applied successively permitting them to be more certain. An additional aspect of the invention contemplates autoniati release of final selector used in establishing a no test connection.

' T is final selector oi the present invention is positioned on the called line under control of an external line relay. lVith the brushes positioned. on the terminals or the wanted line. a relay is'first connected to the sleeve terminal oi the line to test whether Serial No. 132,087.

it is open or has a low resistance unstandard ground connected thereto. It open, or if such ground is present, this relay fails to operate and the sequence switch is arrested in position to cause the operation of an alarm. If no false ground is present, the relay operates and the line is then tested to see whether it is a busy P. B. X. line. The relay for making this test operates under all other conditions. It the. tested line is a busy P. B. X. trunk, or if the line is being tested simultaneously by two final selectors, the selector will be advanced to hunt for an idle P. B. X. trunk, it one exists, in the group. If no idle trunks are present in the group, the selector will stop on the last P. B. X. trunk whether or not it is being simultaneously tested by other final selectors. hen the selector comes to rest the lin will be tested for busy or idle condition. A busy line will cause the restoration of the selector and the transmission of a busy signal to the calling subscriber.

On a completed call to an idle line, disconnection is under the control of the called station. A connection with a line which tests busy to a service connection, is possible through the aid or a cordless operator's incoming selector, which automatically cancels the tests of the line by prematurely operating one of the test relays. \Vhen such a no test connection has been made. the incoming selector reoperates this test relay and releases the final selector which has been used for the no test call without waiting for the called subscriber to hang u).

The drawings consist of Fig. 1 which shows an incoming selector adapted for extending no test connections and Fig. .2 which shows the final selector embodying the present invention.

The operation of a final select r in the course of a service connection will first be described. Assuming that the subscriber at substation 1S0 desires to converse with the subscriber at station 280, he will remove his receiver from the switchhook whereupon line switch 101 extends the calling. line to district selector 102 which operates under the control of senoer 104C to select an idle incoming selector, such as selector 103. Se

lector 103 will then be operated to select an idle linal selector in the desired group, for example, selector 281. Since final selector 281 is in all respects the same as that shown in detail the further ertensionoil' the connection will he described in connection with that selector. For a complete showing of the establishment ofa connection to an incoming selector, reference is made to U. S. Patent 1,589,402 granted to O. H. Kopp, June 22, 1926 and. for the operation of an incoming selector, particularly adapted to function with this final selector, reference may be made to the application of C. H. Berry, Serial No. 182,338, filed Aug. 80, 1926.

hen incoming selections have been completed and the brushes brought to rest on the terminals of the final selector. a fnmlamental circuit established, including a relay of the incoming selector and the stepping relay of the sender. The operation of the relay in the incoming selector connects battery to tip conductor 201 through a predetermined resistance. This battery serves to complete a fundamental circuit which extends from conductor 201 over the left contacts of cam 202, resistance 203, right contact of cam 1, right winding of relay 205, right contacts of cam 207 to ground. Relay 205 operates inthis circuit and locks in a circuit which extends from the right winding of relay 205 over the left contacts of cam 206, right front contact of relay 205, left contact of cam upper right contact of cam 225 to ground. The operation of relay 205 closes a circuit from battery through the winding of relay 208, lower left and upper right con tacts of cam 210, left front contact of relay 205 to ground. Relay 20S locks in turn in a circuit through its Winding over the left contacts of cam 209, right front contact of relay 208, upper contacts of cam 211, contact 212 of jack 213, to ground applied to sleeve conductor 21% by the incoming selector.

This locking circuit remains closed until sequence switch 200 leaves position 6. The operation of relay 208 at this time closes a circuit from battery through the winding of final selector sequence switch magnet 200, lower contacts of cam 215, to ground at the left front contact of relay 20S, zulvancingr the sequence switch to position 2.

With sequence switch 200 in position 2, a. circuit is closed for high :'-'peed-up drive magnet 216 extending from battery through the winding of magnet 2.16. upper left cou tact of cam 217, upper right contact 210. left front Contact of relay 205 to ground. Under the control of magnet 2.16 the final selector is driven upward in a brush select ing movement. As brush 221 passes over commutator strip 220, circuit is intermittently closed from ground over the lower right contact of cam 222, brush 221, commutator strip 220, left contacts of cam 219,

to ring conductor 218. This circuit serves to hold the relay of the incoming selector operated and shunt the stepping relay of the sender in the usual manner. ,Vhen the sender is satisfied, the incoming selector relay releases, removing battery from conductor 218 and relay 205 in turn releases, opening the circuit of magnet 216 and bringing the selector brushes to rest in position to trip the desired set of brushes. lVith relay 205 released a circuit is closed from battery through the winding of sequence switch magnet 200, lower left contact of cam 223, to ground at the left back contact of relay 205, advancing the sequence switch to posi-- tion 3, v

When the fundamental circuit is again established by the sender, battery is connected to the conductor 201, relay 205 is operated and locked, and the sequence switch 200 advanced to position 4., in a circuit extending over the upper contacts of cam 210 to ground at the left front contact of relay 205. High speed magnet 216 is again operated in the previously traced circuit and while the selector is group hunting, an intermittent circuit is completed to conductor 218 over the lower left and upper right contacts of cam 219, commutator strip 227, brush 228 from ground over the right contacts of cam 210 and the left front contact of relay 205. Trip magnet 226 is operated in positions 3 to 5 of sequence switch 200, in a circuit from battery through its winding to ground at the lower left contact of cam 222, so that when the selector is moved upward under the control of magnet 216 the selected set of brushes is tripped. When the sender satisfied, battery is removed from conductor 201, relay 205 released, up-drive magnet stopped, and the sequence switch advanced to position 5.

When the fundamental circuit is 'estah lished for units selection with the final selec tor sequence switch in position 5, relay 205 is operated as before and locked. The operation of relay 205 advances the sequence switch to position 6. The operation of relay 205 also completes a circuit from battery through the winding of low speed updrive magnet 232. upper right contacts of cams 217 and 210 to ground atthe left front contact of relay 205.

In position 6 an intermittent circuit. is connected to conductor 218 over the left contacts of cam 21.), comunitator strip 220. brush 221. lower rightcontact of cam 222 to ground. lVhen the sender is satisfied. battery is removed from conductor 201, and relay 205 releases stopping the upward movement of the selector and advancing the sequence switch to position Relay 233 operates, ifconditions are normal, in position 6%. The holding circuit of relay 208 is transferred in position 6 to the baclr conwill operate in position front contact of relay 200,

tact of relay 237 and left front contact of relay 208 which circuit continues through position 10 or until relay 23. operates.

Sequence switch 200 is now advanced from position 7 to position 9 in a circuit extending from battery through the winding of magnet 200, upper left and lower right contacts of cam 210 lower right contact of cam to ground.

When sequence switch 200 was in positions 6% to 8 inclusive, a circuit was closed from ground through winding of relay 233, lower contacts of cam 211 to sleeve, brush 234. If the called line is in normal condition, battery will be found to be connected to the sleeve terminal through the cut-off relay of the subscribers line, or if the line is busy, the cut-off relay will be found to be connected to ground through a resistance. Relay 233 it to 8 unless the sleeve conductor is open or is grounded through a very low resistance such as would occur if the sleeve were accident-ally grounded. If either of these last two abnormal eonditionsexists, relay 233 does not operate, and the circuit for operating relay 205 is left open. lVhen sequence switch 200 reaches position 9 with relay 205 deenergized, no circuit is provided for advancing the sequence switch out of that position and an alarm is operated over cam 253 after an interval. The release of the selector is brought about manually after discovery of such an abnormal condition.

After relay 233 operates, and as soon as sequence switch 200 reaches position 7 a circuit is closed from battery through the left winding of relay 205, upper contact of cam 229, right winding of relay 205, the

upper contacts of cam 215; back contact of relay 237, left front contact of relay 208 to ground. Relay 205 operates in the circuit above traced and locks in a circuit through its two windings, left contacts of cam 206, right front contact of. relay 205, left contact of cam 22 i, upper right contact of cam 225 to ground, until the sequence switch reaches position 9%.

From the time that relay 205 releases with the sequence switch'in position 0 following units selection until the sequence switch leaves position 8 ground is con-- nected to conductor .218 over the lower con tacts of cam 219. right-back contact of relay 205. upper left contact of cam 224:, upper right contact of cam or, as soon as position 7 reached, over the lower contacts of cam 219 and the upper right contact of cam 222.

As the sequence switch passes through position 8+8 g/ ground. is connected to conductor 201 over the lower right and upper right contacts of cam 202. left contacts of cam 210, and the lower right contact of cam 222. These two grounds serve to advance the incoming selector to bring the selectors into talking position and release the sender.

\Vith relay 205 operated, a circuit is closed for advancing from position 9 to position 10. extending from battery through the winding of magnet 200, upper contacts of cam 210. left front contact of relay 205 to ground.

While the, sequence switch is moved through positions 8 to 10, a test circuit is closed from sleeve brush 23%, lower right and upper left contacts of cum 211, right front contact of relay 208, right contact of cam 23S, winding of relay 237, lower contact of cam 225 to ground.

If brush 234 is resting on the terminal of a busy line in a group leading to a private branch exchange. battery will be connected to the terminal through a resistance of 2600 ohms and ground will also be connected thereto through a resistance of 112 ohms. Relay is marginal so that it will not operate through so high a resistance in parallel with the busy ground or in parallel with another l. l). X. test relay. In consequence relay 20b remains operated in the locking circuit previously traced. clay 205 also remains operated through position 9% to ground at cam and through position 10 in a circuit which extends previously traced to the upper left contact of cam 20(3, and is completed in this position over the lower right contact of cam 200 to ground at the left front contact of relay 205. \Vith relay 208 operated in position 10 a circuit again completed from battery through the winding of low speed updrive magnet. 232, upper right and lower left contacts of cam 217 to ground at the left front contact of relay 20S.

\Vhen an idle line is encountered no groui'id will be connected to the sleeve terminal and the current willbe suthcient to operate relay 237. Relay 237 also operates through the lower resistances connected to the sleeve of individual lines and last lines of P. B. X. groups whether busy or not. The resistance used with the last line of a P. 1%. X. group is made less than for an individual line by the use of a non-inductive shunt around the winding of the cut-off relay so that relay 237 may operate quickly to stop the selector on the last line of the group whether busy or not. The operation of relay 237 opens the holding circuit of relay 208 which in turn opens the circuit of magnet 232 bringing the selector to rest. An additional holding circuit for relay 208 exists at this time from ground at the left front contact of relay 208. lower left contact of cam 217. lower right contact of ram 210. brush 24,0. commutator strip 239, upper right and lower left contacts of cain 209 to the winding of relay 208 which insures that relay 208 will remain energized until the brush set is propback contact of relay 208, upper left and lower right contacts of cam 211., to the sleeve brush as temporary busy condition.

If the line is busy while sequence switch 200 is passing through positions to 10%, a circuit is closed from battery through the left winding of relay 205, upper contact of cam 229, right winding of relay 205, left contacts of cam 200, right front contact of relay 205, left contact of cam 22d, resistance 246, upper contacts of cam 2 11, right back contact of relay 208, upper left and lower right- 7 contacts of cam 211, to the sleeve brush 254.

If the line on which the brushes are standing is busy, ground will be connected to the sleeve terminal from the equipment with which it is engaged and relay 205 will be held operated when the sequence switch reaches position 10%. The only busy line of a P. B. X. group on which the selector be permitted to come to rest would be the last line which has a sutlic1ently low resist- 'ance to operate relay 237 even though busy.

If the line is busy, relay 205 will lock over the upper left and lower right contacts of cam 206 to ground at the left front contactof relay 205 through position 12. The operations following will be described later.

Assuming that the line is idle, as soon as the sequence switch leaves position 10, relay 205 will release and connect ground from the upper right contact of cam 222 over its right back contact, leftcontact of cam 224- through resistance 2&6 to sleeve brush 234: over the path previously described.

When the sequence switch reaches position 12, with relay 205 released, relay 208 is operated in a circuit through its winding, lower left contact of cam 209, upper right contact of cam 2&2, to ground at the left baclr contact of relay 205. Relay 208 in operatingcloses a circuit from battery through the winding of sequence switch magnet 200, lower contacts of am 215, left front contact of relay 208 to ground, advancing the sequence switch to the talking position 13.

As soon as the sequence switch reaches talking position 18, ground is connected over the upper right contact of cam 225, through resistance 2% and the right contacts of cam 241, to the sleeve brush to hold it busy throughout conversation. Relay 208 when operated in position 12 locks over the left position 15 1 contacts of cam 209, right front contact of relay 208, upper contacts of cam 211, con tact 212 of jack 213, over the sleeve conductor 214C to the incoming selector.

At the end of conversation, the release of the connection by the calling subscri er rcstores selectors 102 and 103 and removes ground from conductor 214:, permitting relay 208 to release and advancing sequence switch 200 to position 16 in a circuit from battery throughthc winding of magnet 200, upper left contact of cam 223, to ground at the left back contact of relay 208.

In positions 15 to 15 a circuit is closed from battery through the left winding of relay 205, upper contact of cum 229, right winding of relay 205, uppercontacts of earn 207, back contact of relay 237, lower left contact of cam 21?, lower right contact of cam 210, to ground at the lower right con tact of cam 222. Provided the called sul scriber has not restored his receiver to the switchhook, relay 205 locks in a circuit extending through its two windings, as pre viously traced, left Contacts of earn 206, right front contact of relay 205, upper right contact of cam 22%, over the called su ascribens loop, back to the right contacts of earn 202, left front contact of relay 205 to ground. If the called subscriber still fails to hang up his receiver, interrupter 243 will close its upper contact after an interval, completing a circuit thereover, over'the upper left con tact of cam 242, and lower left contact of cam 209 through the winding of relay 208 to battery. Relay 208 operates and corn pletes a cicuit through the'winding of sequence switch magnet 200, upper left contact of cam 210, lower left contact of cam 21?, to ground the left front contact of relay 208 advancing the sequence witch to position 17, releasing relay 208. After a predetermined interval, interrupter 243 close' its lower contact and extends a circuit thereover from ground over. the lower left contact of cam 2&2 and thence as traced through the winding of relay 208. The operation of relay 208 again advances the sequence switch, this time in position 18 When the sequence switch leaves position 17, the holding circuit of rela 205 is opened. and that relay releases.

If the called subscriber hangs up at the same time as the calling subscriber, the loching circuit above described for relay 205 will be open and that relay will release following Sequence switch 200 is then. advanced to position 18 in a circuit. over the lower left contact of cam 223 to ground at the left back contact of relay 205.

In position 18 a circuit is closed for downdrive magnet 24%, extending over the lower right contacts of cams 217, 210 and'222 to ground. normal under the control of magnet 2&4, trip lhe selector switch is restored to magnet 226 being operated. \Vhen it reaches its normal position, a circuit is closed from battery through the winding of sequence switch magnet 200, lower right contact of cam 223, brush 228 to ground atthe lower right contactof cam 222, advancing the sequence switch to normal.

As soon as the incoming selector released relay 208 in position 13 of sequence switch 200, ground was connected to sleeve conductor 214, over the lower contact of cam winding of relay .137, lower left contact of cam 238, right back contact of relay 208, upper contacts of cam 211, contact of jack 213 to conductor 214:. This ground serves to mark the linal selector busy to any incoming selector. The previously traced circuitlilrewise functions in connection with a no test call which will be described hereinafter. lV hen sequence switch 200 arrived in position 16, ground over the leftcontact of cam 225 was substituted for ground through the winding of relay 237 to continue the busy conditionuntil the final selector is ready for use again.

If the called line had been busy, relay 205 would operate and lock as previously described and remain operated when the switch reached position 12. \Vith relay 205 operated a circuitis closed in position 12 through the winding of down-drive magnet 2-1 1, lower left contact of cam 21?, upper right contact of cam 210 to ground at the left front contact of relay 205. The final selector is restored to normal under the control of magnet 244, the trip magnet also being operated at this time. When the linal selector reaches normal, a circuit is closed from battery through the winding of relay 208, lower contacts of cam 200, normal commutator segment 215, brush to ground L-aJK' at. the lower right contact of cam ltelay 208 locks on its front contact to cam and to sleeve conductor 21luntil the calli g subscriber hangs up. The operation of relay 20S advances sequence switch 200 to position 13 as previously described. 'With the selector switch normal a circuit is closed from battery through the winding of magnet 200, lower right contact of cam 223, normal segment 245, brush 228 to ground at the lower right contact of cam 222, advancing the sequence switch to position 1.

When the sequence switch leave-s position 12, the holding circuit of relay 205 is opened and relay 205 releases. \Vith relay 205 released and sequence switch 200 in position 14, a circuit is closed from ground through interrupter 2 17, lower left contact of cam 229, left winding of relay 205 to bat tery causing relay 205 to operate inter-min tently. On each operation of relay 205 a circuit is closed from ground throrgrh the secondary of tone coil 21S, upper contact of normal connnutator segment 215,-

cam 204, resistance 208, upper right and lower left contacts of cam 206, right front contact of relay 205, lower contact of cam 224, to ring conductor 21S transmitting to the calling subscriber an interrupted tone indicative of the fact that the line is busy. \Vhen. the calling subscriber restores his receiver in response to this signal, relay 208 releases advancing the sequence switch to position 16 as previously described. Since the selector is normal at this time, a circuit will be closed from battery through the sequence switch magnet 200, lower right contact of cam 223, normal segment 24-5, brush 228 to ground at the right contact of cam 222, advancing the sequence switch to position. 1 and restoring the final selector completely to normal.

The extension of a no test call will now be described. A no test connection will usually be made when a subscribers line remains busy to incoming calls over an unusual period of time or when for any reason conditions seem abnormal in connection therewith. It will be assumed, therefore, that a connection has been established between the subscriber at substation 180 and the sub scriber at substation 280 extending through line switch 101, district selector 102, incom-.

ing selector 103, and final selector 201. under the control of sender 10% as above described. Suppose now that the subscriber at substation 105 attempts a connection with the subscriber at substation 280 and finds the line busy. If this condition continues so that there seems to be some emergency involved in the prolonged busy condition of the line, he may use his line switch 106 and the district selector 107 under control of sender 108 to establish a connection with an operators position at which selector 10? appears in jack 109. Associated with this jack is a. signal (not shown) to which the operator responds by plugging the answering plug of cord 1.10 into jack 100. The subscriber may then explain his dii'ticulty to the operator and she will then insert the call ing plug of her cord 110 in jack 112. This jack is connected with a trunk which is especially adapted for extending no test *alls and which terminates in an incoming selector at the ofiice in which the wanted subscriber is located. This trunk appears at a cordless operators position in the incoming oflice in a pair of lamps and a pair of keys.

The battery connected to the sleeve of the calling plug 111 will complete a circuit over the sleeve of jack 112 through the winding of sleeve relay 113 to ground. Relay 113 operates and completes a circuit from battery through the winding of relay 114-. front contact of relay 113, lower contact of cam 115 to ground through an auxiliary alarm circuit (not shown). It also 'closcs closes a circuit from battery through white lamp 118, lower contacts of cam 119, is t front contact of relay 116, lower contacts of cam 120, to ground at the upper right contact of cam 121. The lighting of lamp 118 informs the cordless operator at whose position the incoming selector appears in lamps 118 and 122 and keys 123 and 124- that a call is awaiting attention.

In response to the lighting of lamp 118,

the cordless operator will depress key connecting ground over the right contacts of key 124, right contacts of earn 125, winding of relay 126 to battery. Relay 126 operates and locks over its inner left front contact, upper left and lower right contacts of cam 120 to ground at the upper right contact of cam 121. Relay 126 closes a circuit from battery through the winding of seuence switch ma net uaaer ri ht contact of cam 128, to ground at the middle left contact of'relay 126, advancing the sequence switch to position 2. In addition relay 126 connects the cordless operators telephone circuit to the trunk and starts the zip tone which is associated with the operators telephone. This tone consists of two short impulses of tone which are transmitted to cord and the A operators telephone set connected therewith (not shown) informing the A operator that the cordless operator is ready to receive her instruct-ions. The A operator will then inform'the cordless operator of the wanted number.

hen sequence switch 100 reaches position l%, a locking circuit is' closed for relay 11 1 extending over the front contact of relay 113, upper contact of cam to, ground at the front contact of relay 11 1. In position 2, ground is connected to conductor 132 over the left contacts of cam and the right back contact of relay 137; to conductor 136 over the left contacts of cam 130 and the upper left contact of cam 129; and to conductor 134 over the lower right and upper left contacts of cam 138 and the left back contact of relay 137. These grounds serve to cause the link circuit to operate to associate a cordless sender with the trunk. Ground is also removed from conductor, to identify the trunk to the link circuit. The'operation of a link circuit and sender is disclosed in U. S. Patent 1,345,016 granted to A. E'Lundell et at, June 29. 1920. With the incoming selector sequence switch in v therewith. the link c rcuit finds the trunk, it connects ground to conductor 133 to mark the trunk as busy to other link circuits. When the last digit of the wanted number has been recorded, ground is, connected conductor 131 and a circuit is'completed extending over the back was t 4 7- 111 1. m- 1 f Ms e contact or relay 1 lower -e t con (.L- or cam 128, to the winding of sequence ch magnet 1OO, ad 'anc1ng the sequence switch to position 3. l t hen the "sequence switch leaves position 2, the circuit of white lamp 118 is opened and the lamp extinguished to indicate that the sender has been set. 1

lVith thesequence switch iii-position 3,

ground is removed from conductors 13d and 136 and ground is connected to conductor 133 over the lower left contact of cam 121 independent of the link circuit. 1 ith quence'switchlOO in position 3 the circuit is ready to start selections. This incoming selector also opera es in connection ith an external line relay which in this instance is located in the link circuit, asin the disclosure of the above mentioned patent to Lundell, et al. The line relay operates in a fundamental circuit connecting the link and the sender which is similar to the well known fundamental circuit employed in connection with internal. line relays and includes the stepping relay of the sender.

The line relay of the link oper tee and locks. and is held by commutator pulses which re lease the stepping relay, of the sender in the usual manner. This line relay operates a relay in the incoming selector-cir .iit as will be described to operate the sequence swi ch and the drive magnet controlling the selector. t also controls the final ctor in a similar manner. t is believed that this brief description of the external line relay in connection with the Lundell et al. patent will be sufiicient for the purposes of this disclosure.

lVhen the sender is ready to control incoming brush selection, the line relay in the link operates and connects ground to conductor 135 completing a circuit over the lower right and upper left conductor of cam 117, right winding of relay 116 to battery. Relay 116 operates and closes a circuit from battery through the winding sequence switch magnet 100, lower right contact of cam 145, left front contact of relay 116, to ground at t contact of cam 129,

sel-

the lower lei advancing the sequence swltch to position 4.

Relay 110 is held operated in position l- 1n a circuit extending from battery through its i czun 11?.

right- Wind nq lett contacts right front (201 tacts of can] 141;

l' l l LlIr relay 11o i 4 l" 1" +Q-' closet non outcry 0t up-urire magnet lower left contacts contact 01 relay 1 left contact of Quill v r 136 ore 1-30, strip 119 brush 150, up er right conn t of corn 121 to ground. 11s S-lOOYQ er:-

1 relay 0 relu s 1n the Well horn n'unner.

been received to c or 13; releasing relay 116. Th

elay 1 6 opens the circuit of and brings tie selector to trip the proper set or" u circuit troni battery the winding of sequence switch meget 10o l t e ntzicts of cum 1 11, lets Deck correct relay 116, to ground at the lower eft con- C 0t earn 129 admiringthe s quence the sequence 1'"l 1) epc 1' right concnct or": can

lVhen the sender is ready for the next sel ction, *elu 116 is again operated and locks to conductor 135.

It again closes over its left front contact, the circuit for ud- Ye-ncing sequence switch 100 which now o position 6. in position 6, the uplet 1%? is ooernted as before, ud 1 ineonrirg selector in its group As the switch mores p e selected set of brushes is tripped due to the ouerntion of magnetthis time g rorid is intermittently connected to conductor 1.36 or r thelower contacts commutator strip 143%, hrush per right contact of earn 121, to Vhen the sender is satisfied the circuit of relay 116 is opened. hut held operated in a circuit e3;- from battery through right mind- N of relay 116, left collects of czun 11'? ht front contact or relay 11:") lower concam 15 1, t e upper r strip 156 r con niututor strip over c ntucts 0t can] 119 speetirely to ground at (he upper right coutuct 0t ruin 1:21. These commutator {TIPS serve to insure that the selector bru hes are centered on the terminals ot the outgoing to a final selector before the u :1- d e is slopsed. "When the brushes a properly 1 opens the circuit of inn ret 1 18 the brushes to rest. [Th release 11? on, l 1" i 1 'r 1. 0 ain closes 1e enter our 1).

t by which sequence switch 1, (u (1, moving the sequence switch to posin the sequence switch reaches posiu circuit is closed from hi.

157 to ground. i u g m 116 coses [11? pro i v 11 elu 3,

self ex right and lower lei't lower i'elector to hunt tor :51 id ',l an idle outgoing trunk i re? ground will he pres eye and relay 116 W111 release opening cuit of the rip-drive magnetand tln incoming selector to rest on trunk soon as the holdingcircuit its left Winding, ri L cor tucts 0'? and coininututor st is opened due to tire correct centering oi the h: ush set.

' the sequence r As soon Icr reler 1 J connected to sleeve hrush over the upper right 1211f lower left contacts ot cum 1 right heel: cont: ct of reluy 11 1 iron ground it the upper let't contact of coin 121 When eqrence switch 100 reecles p0 'ition round is connected to sleeve brush 158 tire upper left Contact of r i the final sele'rtor busy to oth with the sequence switch in position 9 relay 116 is operuted on its left windin in the nine circuit in that closed in non ion st 7 and locks in a circuit through its P 1 4 l llpjilr Wincing let-t contacts of earn 117 rigrh-tv front contact of relay 116, upper contacts 4 selector of cum 138, left back contact of relay 137 to ground. In operating relay 11S closes a circuit for sequence switch magnet 1100, acvancing the sequence switch to position The incoming selector remains in this position while the final selector is being operated.

lVith sequence switch 100 in position 10, conductor is extended over the lower left and upper right contacts earn and brush 161 to the line conductor the final selector. Similarly conductor 135 is extended over the right contacts of cum 154: and brush 160 to the tip conductor 201 of the fina selector. The extension. of these conductors permits the operation of the final under control oi. the previouslr described lino relay in the link circuit.

it this time the line relay connects hattery through the proper resistance to con ductor 135 and therefore to conductor opera H relay 205. The subsequent operations of the final selector take place as described shore in a service connection until sequence so ui-ch 200 is ad anced from position 6 to position '7, following final units selectim. Relay 205 is released in position 6,- by the sender. Ground is connected to the sleeve eondu tor 2143: by earn 225 as previously described.

As soon as the .nal selections are com plot-ed ground is connected fron'i the sender to conductor 131 orer the l .cl; con a't of relay 14:1, lower left contact of cam 2'. left winding of relay 137 to battery. Relay 13? operates in thiscircuit anl locks in a circuit through its right winding and right front contact, left conta of com 130, lower left and upper 1' t contacts of cani 152, brush 1G1 conductor 218, lower contacts of cam 219 over the right back contact of re- 205 left contaft of cam 22% upper right contact can: 225 to a ound in position 6 Qperat-ion of relay operates which breaks the circuit through 1e left windings of relay Li-3?. As soon as final selector sequence switch reaches this circuit also grouiuled per right contact of car-n in '0 8 3 of sequence switch 200.

r "ll.

itiine the operation of relay ground over its left front conta t unner left and lower right contacts of to conductor and thence to conductor 201, completing acircuit fro a hattery through resistance winding of relay 23?, lower left contact of earn 20%, resistance 203, left contacts of cam 202 to conductor 201, operating rel y 297 at posi- 1A); tion only of sequence switch 200. It will be ren'ieinhered that the locking circuit of relay 208 which'is established soon as sequence switch 200 reaches position 6 eze tends orer the back contact of relay 237. With relay 237 operated as the sequenqe switch pass-es through position this locking circuit is opened and relay 208 releases. Sequence switch 200 is advanced from position 7 position 9 in a circuit entenuing from battery through the winding of magnet 200, upper left and lower right contacts of earn 210 to ground at the lower right contact of can'i222. lVith relay 208 released sequence switch 200 is immediately advanced out of position 9 to pos tion 12, the circuit extending over the upper left contact of earn 223 to ground at the l ft back contact of relay Sequence switch 290 will therefore be advanced out of pos 'on 9 whether the sl eve condition is normal. or not and the test circuit of relay 2533 will he l1lQllC- tire. Similarly, the test whether the called line is one of a P. B. X, group and busy, is

cancelled sinze the circuit for relay 23 13 new open at the contact relay 208. In

or rel; from battery through its winding left contacts of cum 209, right front contact of rel 20S, upper contacts of earn 211, contact of jack 213, sleere conductor 214., brush 158 to ground at the upper left contact of cam 15?. Relay 208 in operating advances sequence switch 200 to position 13 in a circuit extending through the winding of magnet 200 lower contacts of earn 215 to ground at the left front contact of relay 208.

Position 13 is the talking position of he final selector and the sequence switch remains in that position until the selector is released. In the meantime, tne operation of relay 137 in position 10 of sequence switch and position 6 to 8 of sequence switch 200 opens the holding circuit of relay 116 and closes a circuit from battery through the winding of relay 1 l1 lower contacts of can: 162, to ground at the outer right front contact of relay 1S7. llith relay 137 operated. ground is disconnected from conductor 132 and the sender and link dismissed. 1n positions 11 to 18 of sequence switch 100 the circuit of green lamp 122 will be extended directly to ground over the right contact of cam 129. 7

When the final selector sequence switch leaves position 8 4, ground is disconnected from conductor 218 and the locking circuit of relay 137 is therefore opened, permit-ting that relay to release. lVith relays 137 and 116 both released a circuitis closed from ground over the left back contact of relay 137, left contacts of earn 138, left back ion contact of relay 116,10wer contacts of cam 144, winding of sequence switch magnet 100 to battery, advancing the sequence switch from position 10 to position 12 which is the talking position for the incoming selector. The tip conductor 201 in position 12 is extended over brush 160 and the lower contacts of cam 154 through condenser 164, to the tip of jack 112 and cord 110. Ring conductor 218 is extended over brush 161, upper contacts of cam 152 through condenser 165 to the ring of jack 112 and cord 110.

The A operator may now listen in on the called line, challenge on the line or make whatever simple test may seem necessary to determine the condition thereof. Having reached a conclusion, she will then transmit the information to the subscriber at substation 105 and will then withdraw her cord from jacks 109 and 112.

The withdrawal of plug 111 opens the circuitof relay 113 and that relay releases relay 114. Relay 114 released closes a circuit from battery through the left winding of relay 137, lower contacts of cam 139 to ground at the right back contact of relay 114, Relay 137 operates and closes a circuit from battery through the winding of sequence switch magnet 100, upper left contact of cam 128 to ground at the left frontcontact of relay 137, advancing the sequence switch to position 14.

As sequence switch 100 leaves position 12 the ground which was connected over the upper left contact of cam 157 to the sleeve brush 158 is removed and relay 208 in the final selector releases. With relay 208 released, a circuit is closed from battery through right winding of relay 137 and its inner right front contact, lower contacts of cam 130, sleeve brush 158, terminal 163, conductor 214, contact 212 of jack 213, upper contacts of cam 211, right back contact of relay 208, lower left contact of cam 238, winding of relay 237, to ground at the lower contact of cam 225, operating relay 237 and holding relay 137 operated. It is to be noted that the energizing circuit of relay 137 was held closed until sequence switch 100 left position 13 afiording sufficient time for the closure of this holding circuit. Likewise, it should be noted that battery through resistance 166 is connected in parallel with the winding of relay 137, and ground through resistance 251 is connected in parallel with relay 237 so that relay 237 will operate and only operate during release from a no-test connection.

It will be remembered that during the courseof a regular call, in positions 15 to 15 of the final selector, relay 205 is connected over the loop of the called line to prevent the release of the final selector as long as the receiver is off the switchhook at the called station. The operation of relay 237 at this time opens this circuit for operating relay 205 and hence permits the release of the final selector independent of the called subscriber. The release of relay 208 following position 12 of sequence switch 100 also closes a circuit from battery through the winding of sequence switch magnet 200, upper left contact of cam 223, to ground at the left back contact of relay 208, advancing the sequence switch 200 from position 13 to position 16. Since relay 205 is non-operated at this time, a circuit is at once closed from battery through the winding of magnet 200, lower left contact of cam 223 to ground at the left back contact of relay 205 and the sequence switch is advanced to position 18.

When the sequence switch 200 reaches position 16 the circuit through relay 237 is opened and direct ground over the left contact of cam 225 is connected to sleeve conductor 214 to hold relay 137 operated until the final selector sequence switch leaves position 18. In position 18, the down-drive magnet 244 is operated as previously described and the selector restored to normal whereupon sequence switch 200 is advanced to position 1.

.Vhen sequence switch 200 leaves position 18, ground is disconnected from the Sleeve conductor 214, and relay 137 is permitted to release. The release of relay 137 closes a circuit from battery through the winding of sequence switch magnet 100, upper left contact of cam 145 to ground at the right back contact of relay 137 advancing the sequence switch to position 15. A circuit is then closed from battery through the winding of sequence switch magnet 100, upper right contact of cam 145 to ground at the right back contact of relay 114 advancing the sequence switch to position 18.

In position 18 an obvious circuit is closed for down-drive magnet 167 and the incoming selector is returned to normal under the control of that magnet. Vhen it reaches normal position, a circuit is closed from battery through the winding of magnet 100, lower left contact of cam 145, normal commutator segment 146, brush 147 to ground at the upper right contact of cam 121, advancing the sequence switch to position 1. The incoming and final selectors are now normal. The green lamp 122 remains lighted steadily until. sequence switch 127 leaves position 18 whereupon that lamp is also extinguished indicating to the cordless operator that the trunk has been released and has restored to normal.

lvhat is claimed is:

1. In a telephone system, a subscribers line, a selector switch, means in said switch for testing the idle or busy condition of said line, and means for testing for an unstandard condition on the test terminal of said line, said latter means effective if an unstandard condition is encountered to render said first means ineffective.

2. In a telephone system, a subscribers line, a selector switch, means in said switch for testing the idle or'busy condition of said line, a signal, and means for testing for an unstandard condition on the test terminal of said line, vsaid latter means effective if an unstandard condition is encounteredto render said firstmeans ineffective andto operate said signal.

3. In a telephone exchange system, a subscribers line, a selector switch, means in said selector switch for successively applying a plurality of tests to said line, and means controlled by said testing means to permit the completion of a connection to said line.

4. In a telephone exchange system, a subscribers line, a selector switch, a plurality of rela s in said selector switch for applying a p urality of tests to said line. means to successively associate said relays with said line, and means controlled by said relays to permit the completion of a connection with said line.

5. In a telephone system, a subscribers line,a selector switch, means in said switch for testing the idle or busy condition of said line, means operative for rendering said testing means ineffective whereby said selector switch may be caused to establish a con nection with a busy line, and means under the control of sa1d latter means for restoring said switch.

6. In a telephone system, a subsoribers line, a selector switch, means in said switch for testing the idle or busy condition of said line, means operative for rendering said testing means ineffective whereby said selector switch may be caused to establish a connection with a busy line, means normally under the control of said line for causing the restoration of said switch, and means under the control of said second means for causing therestor ation of said swltchirrespectlve of the control of said line.

T. In a telephone system, a' subscribers line, a selector switch, means in said switch for testing for an unstandard condition on the test terminals of said line, means for testing the idle or busy condition of said line, and means operative for rendering both oi said testing means ineitectivewhereby said selector switch may be caused to establish a connection with a line irrespective of its condition.

8. In a telephone exchange system, a subscribers line, a selector switch, a plurality of relays in said selector switch for applying a. plurality of tests to said line, means to successively associate said relays with. said line, means controlled by said relays to permit the completion of a connection with said line, and means to prematurely operateone of said relays to render all 01 said tests ineffective whereby said selector may be caused to establish a connection with a line irrespective of its condition.

S). In a telephone exchange system, a subscribers line, a selector switch, a plurality of relays in said selector switch for applying a plurality of tests to said line, means to successively associate said relays with said line, means controlled by said relays to per mit the completion of a connection with said line, means to prematurely operate one of said relays to render all of said tests inelfeo tive whereby said selector may be caused to establish a connection with a line irrespectire of its'condition, meansnormally under the control of said line for causing the restoration of said switch, and means for re-' operating said relay to cause the restoration of said switch irrespective of the control of said line.

. In witness whereof, I hereunto subscribe my name this 26th-day of August, A. 1).,

lVILLIAM G, JORDAN. 

